A project can contain multiple files which can be opened, closed, and saved together. The types of files that can be contained within a project vary according to the language engine.
Note Solutions can also contain files which are not related to a specific project. These are listed under the Miscellaneous Files node in the Project Explorer. If you attempt to add a file to a project that isn’t appropriate for the project type, it will be added to the Miscellaneous Files node. You can also explicitly add a file to the Miscellaneous Files node using the New File or Open File commands, available from the File menu.
To add a file to a project
The selected item will be added to the selected project in the Project Explorer.
To remove a file from a project
The file will be removed from the project; it will not be deleted however, and can still be used in other projects.